1. Field of the Invention
The present invention relates in general to the field of integrated circuit device mounting techniques and in particular to methods and apparatus for supporting a circuit board from one side while a component is mounted to the second side. Still more particularly the present invention relates to methods and apparatus for supporting a circuit board during mounting of an electronic component which will accommodate misalignment between the circuit board and the support fixture.
2. Description on the Prior Art
The increasing complexity of electronic systems and the concomitant increase in component density has resulted in the common utilization of robotic systems for the manufacturing of such systems. Those skilled in the art will appreciate that robotic systems provide a high degree of efficiency and speed for repetitive operations, such as the mounting of integrated circuit devices to circuit boards.
Many techniques exist for the mounting of electronic components to circuit boards. One such technique is the so-called "hot bar thermode" bonding technique which utilizes a placement head to position an integrated circuit having a plurality of conductive leads at a desired mounting point on a printed circuit board. Thereafter, multiple heat activatable blades are urged into contact with the conductive leads and heated to a point where the electronic component is bonded to the circuit board by means of presoldered connections thereon. Such hot bar thermode bonding requires back-side support of the circuit board or substrate which is capable of withstanding substantial forces. Typically, a force of up to 200 Newtons may be applied during the heating of the thermode blades in order to generate the required heat transfer necessary to melt the solder at the connections.
In known prior art systems a support anvil is typically provided and generally comprises a rigid fixture with a rubber gasket. The rubber gasket was assumed to deliver an even force to the back side of the bond area but it has recently been discovered that where misalignment occurs between the thermode blade and the back side support a significant variation in the force levels along the thermode blade may be generated. This condition is undesirable in that it results in an unreliable mounting of an electronic component.
Additionally, such hot bar thermode bonding tools are typically quite complex in that the heat activatable thermode blades are often resiliently mounted to accommodate such misalignments and the placement head must be capable of accurate positioning of an electronic component while exerting the large forces necessary to accomplish bonding.
It should therefore be apparent that a need exists for an improved method and apparatus for supporting a circuit board during the mounting of an electronic component which will accommodate variations in planarity between the support fixture, the circuit board and the bonding tool. Further, such an improved system should be able to accommodate the presence of electronic components on both sides of a circuit board which can further complicate any attempt at providing support during the mounting of an electronic component.